Pharmacogenetics of osteoporosis: future perspectives

Genetic polymorphisms and their influence on therapeutic response to alendronate-a pilot study

Introduction: Osteoporosis has a strong genetic contribution, and several genes have been shown to influence bone mineral density. Variants in the human genome are considered important causes of differences in drug responses observed in clinical practice. In terms of bone mineral density, about 26–53% of patients do not respond to amino-bisphosphonate therapies, of which alendronate is the most widely used. Material and method: The current study is prospective, observational, analytical, longitudinal and cohort type. It included 25 postmenopausal women treated with alendronate for 1 year. Bone mineral density at lumbar spine and proximal femur was measured and bone turnover markers (C-terminal telopeptide of type I collagen and procollagen 1N-terminal propeptide) were evaluated at 0 and 12 months of treatment. Six single nucleotide polymorphisms in osteoporosis-candidate genes were genotyped (FDPS rs2297480, LRP5 rs3736228, SOST rs1234612, VKORC1 rs9934438, GGPS1 rs10925503 and RANKL rs2277439). Treatment response was evaluated by percentage changes in bone mineral density and bone turnover markers. Results: The heterozygous CT of FDPS rs2297480 showed lower increases in BMD values in the lumbar spine region and the homozygous CC of the GGPS1 rs10925503 showed lower increases in terms of BMD at the total hip region. No association was found for LRP5 rs3736228, SOST rs1234612, VKORC1 rs9934438 and RANKL rs2277439. Conclusions: Romanian postmenopausal women with osteoporosis carrying the CT genotype of FDPS rs2297480 or the CC genotype of GGPS1 rs10925503 could have an unsatisfactory response to alendronate treatment. Key words: osteoporosis; genetic polymorphism; alendronate; bone mineral density; bone turnover markers,

Association Between Geranylgeranyl Pyrophosphate Synthase Gene Polymorphisms and Bone Phenotypes and Response to Alendronate Treatment in Chinese Osteoporotic Women

Objective To investigate the relationship between geranylgeranyl pyrophosphate synthase (GGPPS) gene polymorphisms and bone response to alendronate in Chinese osteoporotic women.Methods A total of 639 postmenopausal women with osteoporosis or osteopenia were included and randomly received treatment of low dose (70 mg per two weeks) or standard dose (70 mg weekly) of alendronate for one year. The six tag single nucleotide polymorphisms of GGPPS gene were identified. Bone mineral density (BMD), serum cross-linked C-telopeptide of type I collagen (β-CTX), and total alkaline phosphatase (ALP) were measured before and after treatment. GGPPS gene polymorphisms and the changes of BMD and bone turnover markers after treatment were analyzed.Results rs10925503 polymorphism of GGPPS gene was correlated to serum β-CTX levels at baseline, and patients with TT genotype had significantly higher serum β-CTX level than those with TC or CC genotype (all P<0.05). No correlation was found between polymorphisms of GGPPS gene and serum total ALP levels, as well as BMD at baseline. After 12 months of treatment, lumbar spine and hip BMD increased and serum bone turnover markers decreased significantly (P<0.01), and without obvious differences between the low dose and standard dose groups (all P>0.05). However, GGPPS gene polymorphisms were uncorrelated to percentage changes of BMD, serum total ALP, and β-CTX levels (all P>0.05).Conclusion GGPPS gene polymorphisms are correlated to osteoclasts activity, but all tag single nucleotide polymorphisms of GGPPS gene have no influence on the skeletal response to alendronate treatment.

Lack of Influence of Vitamin D Receptor BsmI (rs1544410) Polymorphism on the Rate of Bone Loss in a Cohort of Postmenopausal Spanish Women Affected by Osteoporosis and Followed for Five Years

A longitudinal study was conducted to investigate the relation between a polymorphism in the vitamin D receptor (VDR) gene and changes in bone mineral density (BMD) and quantitative ultrasound of the phalanges (QUS) over a five-year period. The subjects were 456 postmenopausal women with osteoporosis undergoing treatment, aged 59.95±7.97 years (mean±standard deviation [SD]) at baseline. BMD was measured at the hips and lumbar spine by dual-energy X-ray absorptiometry, and QUS was measured by means of amplitude-dependent speed of sound (Ad-SoS) at the phalanges. Lifestyle information was obtained via a questionnaire. The genotype frequencies of the BsmI (rs1544410) gene polymorphism were 29.4%, 47.1%, and 23.5% for bb, Bb, and BB, respectively. After five years, BMD (annual change in %/year) at the femoral neck (FN) showed a significant modification based on the rs1544410 genotype (BB vs Bb); there was an overall decrease in bone mass (-0.70±2.79%/year; P = 0.025). An analysis of covariance with adjustments for age, weight, height, percentage of weight change per year, baseline BMD and calcium intake showed that the observed associations were no longer significant (P = 0.429). No significant associations were found between the QUS measurements and the rs1544410 genotype after the five-year period. Our study limitations includes lack of information about type and length of duration of the osteoporosis treatment. Our results indicate that rs1544410 polymorphisms do not account significantly for the changes in bone mass in Spanish women with osteoporosis undergoing treatment.

SOST polymorphisms and response to alendronate treatment in postmenopausal Chinese women with osteoporosis

AIM

To investigate the association between SOST gene polymorphisms and response to alendronate treatment.

MATERIALS & METHODS

639 Chinese postmenopausal women with osteoporosis or osteopenia received alendronate treatment. Polymorphisms of SOST were analyzed. Bone mineral density (BMD), serum ALP and β-CTX levels were measured. The correlation of SOST polymorphisms with changes of BMD and bone biomarkers after treatment was analyzed.

RESULTS

rs1234612 and rs851054 polymorphisms were correlated to baseline lumbar spine BMD (p < 0.05). After 12 months of treatment rs1234612 and rs865429 polymorphisms were correlated to BMD changes at the lumbar spine (p < 0.05) or femoral neck (p < 0.05), respectively.

CONCLUSION

The polymorphisms of SOST are genetic factors affecting bone health and response to alendronate in Chinese postmenopausal women.

LRP5 polymorphisms and response to alendronate treatment in Chinese postmenopausal women with osteoporosis

AIM

To investigate the association between LRP5 gene polymorphisms and response to alendronate in Chinese osteoporotic women.

MATERIALS & METHODS

Six hundred and thirty nine Chinese postmenopausal women with osteopenia or osteoporosis were included and received alendronate treatment. The A1330V polymorphism of LRP5 was investigated. Bone mineral density (BMD) and bone turnover markers (ALP and β-isomerized carboxy-telopeptide of type I collagen [β-CTX]) were measured before and after treatment. The correlation of LRP5 polymorphisms with changes in BMD and bone turnover biomarkers were analyzed after treatment.

RESULTS

After 12 months of treatment, participants with CC and CT genotypes had a larger increase in lumbar spine BMD and a larger decrease in serum β-CTX and ALP levels than those with TT genotype (all p < 0.001). No significant genotype-treatment interaction was found in hip BMD.

CONCLUSION

The A1330V polymorphism of LRP5 is possibly correlated with response to alendronate treatment in Chinese women with osteoporosis, and the TT genotype could possibly predict a weak response to alendronate.

Clinical impact of recent genetic discoveries in osteoporosis

Osteoporotic fracture carries an enormous public health burden in terms of mortality and morbidity. Current approaches to identify individuals at high risk for fracture are based on assessment of bone mineral density and presence of other osteoporosis risk factors. Bone mineral density and susceptibility to osteoporotic fractures are highly heritable, and over 60 loci have been robustly associated with one or both traits through genome-wide association studies carried out over the past 7 years. In this review, we discuss opportunities and challenges for incorporating these genetic discoveries into strategies to prevent osteoporotic fracture and translating new insights obtained from these discoveries into development of new therapeutic targets.

Genetic variant in the aquaporin 9 gene is associated with bone mineral density in postmenopausal women

This study investigated whether single nucleotide polymorphisms (SNP) in the aquaporin 9 (AQP9) gene is associated with bone mineral density (BMD) in Thai postmenopausal women, after an initial genome-wide screening using high-throughput SNP genotyping in pooled DNA samples. Subjects consisted of 516 postmenopausal women aged 50 or more. High-throughput SNP screening was performed by comparing the estimated allele frequency derived from hybridization signal intensities of pooled DNA samples on the Affymetrix 500 K SNP genotyping chip set. The SNP was then genotyped for each subject individually. Data were expressed as mean ± SEM. Pooled DNA SNP screening revealed the allele frequency of an intronic A/T SNP rs2414539 in the AQP9 gene as being different between subjects with femoral neck BMD in tertiles 1 and 3. Individual genotyping in all subjects revealed that femoral neck BMD in subjects with TT, TA, and AA genotypes were 0.79 ± 0.06 (n = 3), 0.75 ± 0.01 (n = 98), and 0.71 ± 0.01 g/cm(2) (n = 415), respectively. The presence of the T allele in rs2414539 was associated with femoral neck BMD (r = 0.11, P < 0.05) but not with lumbar spine BMD. The relationship was still significant after controlling for body weight and age (P < 0.05). Genetic variation in the AQP9 gene is associated with femoral neck BMD in postmenopausal women, and may represent one of the susceptibility genes for phenotypes related to bone mass.

Genetic determinants of osteoporosis: common bases to cardiovascular diseases?

Osteoporosis is the most common and serious age-related skeletal disorder, characterized by a low bone mass and bone microarchitectural deterioration, with a consequent increase in bone fragility and susceptibility to spontaneous fractures, and it represents a major worldwide health care problem with important implications for health care costs, morbidity and mortality. Today is well accepted that osteoporosis is a multifactorial disorder caused by the interaction between environment and genes that singularly exert modest effects on bone mass and other aspects of bone strength and fracture risk. The individuation of genetic factors responsible for osteoporosis predisposition and development is fundamental for the disease prevention and for the setting of novel therapies, before fracture occurrence. In the last decades the interest of the Scientific Community has been concentrated in the understanding the genetic bases of this disease but with controversial and/or inconclusive results. This review tries to summarize data on the most representative osteoporosis candidate genes. Moreover, since recently osteoporosis and cardiovascular diseases have shown to share common physiopathological mechanisms, this review also provides information on the current understanding of osteoporosis and cardiovascular diseases common genetic bases.